/**
 * @param {string} s
 * @return {string[]}
 */
 var cellsInRange = function(s) {
  const hash = ch => ch.charCodeAt() - 'A'.charCodeAt()
  const arr = new Array(26).fill().map(() => new Array())
  let [l, r] = s.split(':')
  let r1 = Number(l[1]), r2 = Number(r[1])
  for(let i = hash(l[0]); i<=hash(r[0]); i++) {
    let c = String.fromCharCode(i + 'A'.charCodeAt())
    for(let j = r1; j<=r2; j++){
      arr[i].push(`${c}${j}`)
    }
  }
  return arr.reduce((pre,cur) => pre.concat(cur), [])
};